bring the solution closer to neutriality

what is a neutralizing agent for NiCAD

Neutralizing Antibody Rapid Test Kits typically utilize a lateral flow immunoassay technique to detect neutralizing antibodies. A small blood sample is collected from the individual, and the test kit contains specific reagents that interact with the neutralizing antibodies. The kit produces visible results, such as color changes or lines, indicating the presence or absence of neutralizing antibodies in the sample.

Its the antigen in a particular foreign body or pathogen that the body recognizes as "allo" or unfamiliar.. Maybe even harmful. So antibodies are produced against these antigens. And since they are 'neutralizing antibodies' it follows that the antigens they bind to are 'neutralizing antigens'